Method for manufacturing semiconductor device having grown layer on insulating layer

ABSTRACT

A semiconductor device is manufactured by forming an epitaxial layer (22) insulated from a silicon substrate (2), and forming a device in the epitaxial layer (22). On the semiconductor substrate (2), a silicon dioxide layer (4) is formed (FIG. 2A). Then the silicon dioxide layer (4) is provided with openings (14) (FIG. 2D). Silicon carbide is grown until it protrudes from the openings (14) to thereby form a silicon carbide seed crystal layer (16) (FIG. 2E). Next, oxidation is carried out, allowing a field oxide layer (20) to be connected at the portion under the openings (14) and the silicon carbide seed crystal layer (16) to be insulated from the silicon substrate (2). Thereafter, epitaxial growth is effected from the silicon carbide seed crystal layer (16). The growth is stopped before silicon grown layers (22) connect to one another, thus obtaining epitaxially grown layers (22) having regions which are separate from one another. The MOS device is formed in this epitaxially grown layer (22). The silicon carbide grown layer (22) is isolated from the silicon substrate (2) and formed as regions isolated from one another, having a uniform plane bearing. Accordingly, the layer (22) causes no electrostatic capacitance due to the absence of a pn junction with the silicon substrate (2) or with an adjacent layer (22), allowing high-speed operation of the device. Moreover, the unique plane bearing facilitates control during the manufacturing process.

This application is a division of application Ser. No. 07/804,576, filedDec. 10, 1991, now U.S. Pat. No. 5,826,991.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods for manufacturing semiconductordevices and, more particularly, to structures having a semiconductorlayer on an insulating layer.

2. Description of the Prior Art

Semiconductor microchips or integrated circuits in general are providedin a structure in which an epitaxially grown layer is formed on asilicon substrate, and circuits are then formed in the epitaxially grownlayer. The silicon substrate and the epitaxially grown layer are joinedtogether to form a pn junction. The resulting capacitance of the pnjunction, however, is such that it reduces the operating speed of thedevice. Accordingly, this structure is not suitable for forming devicesrequiring high-speed operation.

In the last few years, to solve this problem, a way of forming anadditional silicon monocrystal layer to overlie an insulating layer onthe silicon substrate (Semiconductor on Insulator, or SOI, technique)has been sought. This is to eliminate the pn junction between thesemiconductor device formed on the silicon monocrystal layer and thesilicon substrate, by insulating the silicon monocrystal layer from thesilicon substrate.

FIG. 1 illustrates the conventional SOI technique using the ELO(Epitaxial Lateral Overgrowth) method as described in "Lateral EpitaxialOvergrowth of Silicon on SiO₂," by D. D. Rathman et. al., JOURNAL OFELECTRO-CHEMICAL SOCIETY SOLID-STATE SCIENCE AND TECHNOLOGY, October,1982, p. 2303. First, a silicon dioxide layer 4 is grown on top of asemiconductor substrate 2. Then, the silicon dioxide layer 4 is etchedusing photoresist to thereby open seed windows 6 (see FIG. 1A). This isfollowed by selective epitaxial growth of silicon in the longitudinaldirection from the seed windows 6 and, subsequently, lateral epitaxialgrowth, to form an epitaxial layer 8 on the silicon dioxide layer 4 (seeFIG. 1B). By these processes, the pn junction between the epitaxiallayer 8 and the silicon substrate 2 can be reduced in area to the sizeof the seed window 6, thus allowing the pn junction capacitance to bereduced and high-speed operation of the device to be realized.

Another method available is the SENTAXY method which is disclosed in"New SOI-Selective Nucleation Epitaxy," by Ryudai Yonehara et. al.,Preliminary Bulletin for the 48th Fall Academic Lecture 1987 by theApplied Physics Society, 19p-Q-15, p. 583. In this method, a pluralityof crystal-grown silicon nuclei are formed on an insulating layer ofsilicon dioxide or the like, further effecting epitaxial growth fromeach of the nuclei. Methods of forming the nuclei include formation of asmall-area silicon nitride layer composed of the nuclei, or employmentof the FIB (Focused Ion Beam) method. Using this method, the epitaxiallayer and the silicon substrate may be isolated from one another by anoxide layer, which will solve the aforementioned problems.

However, the conventional SOI technique described above has thefollowing disadvantages.

In the ELO method shown in FIG. 1, the junction, although reduced, isnot wholly eliminated. This would arrest further increase of theoperating speed of the device.

In the SENTAXY method, on the other hand, the epitaxial layer and thesilicon substrate are isolated from one another, thus overcoming the ELOmethod disadvantages. However, the SENTAXY method involvesdifferentiation in the plane bearing of the epitaxial layer that growsfrom each of the nuclei. This differentiation in the plane bearing ofthe epitaxial layer causes variation in oxidation rate and othercharacteristics, with the result that a device having desiredcharacteristics cannot be formed uniformly.

SUMMARY OF THE INVENTION

An object of the present invention, therefore, is to overcome theaforementioned problems and disadvantages and provide a semiconductordevice having a grown layer which is isolated from the substrate by aninsulating layer and uniform in plane bearing.

The present invention provides, in a first embodiment, a method formanufacturing a semiconductor device having a grown layer on aninsulating layer, comprising:

an insulating layer formation step of forming an oxide insulating layeron a silicon substrate;

an opening formation step of providing the oxide insulating layer withan opening for seed crystal growth;

a seed crystal growth step of effecting crystal growth until the siliconcarbide seed crystal layer protrudes from the opening with the oxideinsulating layer used as a mask;

a selective oxidation step of oxidizing the silicon substrate under theopening with the silicon carbide seed crystal layer used as a barrier,thereby cutting off the connection between the silicon carbide seedcrystal layer and the silicon substrate;

a silicon carbide growth step of subjecting the silicon carbide tocrystal growth on the basis of the silicon carbide seed crystal layer,to thereby obtain regions of the silicon carbide grown layer separatedfrom one another; and

a device formation step of forming a semiconductor device on the siliconcarbide grown layer.

In another embodiment, a method for manufacturing a semiconductor devicehaving a grown layer on an insulating layer comprises:

an insulating layer formation step of forming an oxide insulating layeron a silicon substrate;

an opening formation step of providing the oxide insulating layer withan opening for seed crystal growth;

a seed crystal growth step of effecting crystal growth until the siliconcarbide seed crystal layer protrudes from the opening with the oxideinsulating layer used as a mask;

an oxide insulating layer removal step of removing the oxide insulatinglayer

a selective oxidation step of oxidizing the silicon substrate under theopening with the silicon carbide seed crystal layer used as a barrier,thereby cutting off the connection between the silicon carbide seedcrystal layer and the silicon substrate;

a silicon carbide growth step of subjecting the silicon carbide tocrystal growth on the basis of the silicon carbide seed crystal layer,to thereby obtain regions of the silicon carbide grown layer separatedfrom one another; and

a device formation step of forming a semiconductor device on the siliconcarbide grown layer.

Also provided is a complementary MOS device which is formed in thesilicon carbide grown layer isolated from the silicon substrate, formedas regions isolated from one another, and has a uniform plane bearing.

While the novel features of the invention are set forth in a generalfashion, particularly in the appended claims, the invention, both as toorganization and content, will be better understood and appreciated,along with other objects and features thereof, from the followingdetailed description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are views illustrating the conventional SOI(Semiconductor on Insulator) technique using the ELO (Epitaxial LateralOvergrowth) method.

FIGS. 2A-2E are views illustrating a method for manufacturing asemiconductor device which is an embodiment of the present invention.

FIGS. 3A-3C show views illustrating a method for manufacturing asemiconductor device which is another embodiment of the presentinvention.

FIG. 4 is a view illustrating an example of the opening 14 provided inthe oxide insulating layer 4 shown in FIG. 2D.

FIG. 5 is a view illustrating another example of the opening 14 providedin the oxide insulating layer 4 shown in FIG. 2D.

FIGS. 6A-6E show views illustrating a method for manufacturing acomplementary MOS device which is an embodiment of the presentinvention.

FIG. 7 is a view illustrating a structure of a complementary MOS devicemanufactured by the steps shown in FIGS. 6A-6E.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A method for manufacturing a semiconductor device according to a firstembodiment of the present invention is shown in FIGS. 2A-2E. First, asilicon substrate 2 is placed in an oxygen atmosphere, with temperatureincreased to high, thereby thermally oxidizing the substrate surface. Asa result, a silicon dioxide layer 4 (SiO₂) serving as an oxideinsulating layer is formed on the top of the silicon substrate 2, asshown in FIG. 2A. Preferably, the silicon dioxide layer is formed thin,for example, approximately 30 to 300 nm thick. Next, as shown in FIG.2B, photoresist 10 is applied onto the silicon dioxide layer 4. After amask is placed on the photoresist 10 and exposed to ultraviolet rays,openings 12 are formed, as shown in FIG. 2C. In this state, with thephotoresist 10 used as a mask, the silicon dioxide layer 4 is subjectedto etching. Subsequently, the photoresist 10 is removed by use of amixed liquid of sulfuric acid and hydrogen peroxide. Thus, openings 14for seed crystal growth are formed, as shown in FIG. 2D. The width ofthe openings 14 is preferably less than 2 μm.

In the step shown in FIG. 2D, the surface of the silicon substrate 2exposed at the area of opening 14 is carbonized. Carbonization isintended to reduce the lattice inconsistency between the siliconsubstrate 2 and the seed crystal layer 16 (3C-SiC) at the next step ofgrowing a silicon carbide layer, that is, to provide a buffer layer bycarbonizing the surface of the silicon substrate 2.

The openings 14 are then selectively subjected to epitaxial growth ofsilicon carbide monocrystal, so that seed crystal layers 16 are formedas shown in FIG. 2E. The epitaxial growth at this step is controlled soas to suppress lateral growth. In this embodiment, the longitudinalgrowth is allowed to range approximately 1 to 4 μm, while the lateralgrowth is suppressed to remain within 1 μm.

During growth of the seed crystal layer 16, there may arise stackingfaults at the interface with the silicon dioxide layer 4. Due to this,the layer 4 of silicon dioxide is formed thin so as to reduce theinterface area, as described above, to prevent stacking faults. Further,the epitaxial growth is preferably carried out at as low a temperatureas possible. Moreover, when the silicon dioxide layer 4 is formed to asilicon substrate (100) in a rectangular pattern in the direction of<100>, stacking faults can be further suppressed. And still further,when a thin polysilicon or nitride silicon layer is added to thesidewall of the silicon dioxide layer 4 prior to the growth in order toimprove the lattice consistency, the crystal faults can also besuppressed. Each of the seed crystal layers 16 formed by the above stepshas the same plane bearing.

After seed crystal layer 16 growth, an oxidation treatment is performed,oxidizing the silicon dioxide layer 4 and the silicon substrate 2, toform the field oxide layer 20. The field oxide layer 20 also growslaterally at its ends (Bird's Beak phenomenon). As a result, the silicondioxide layer 4 connects to one another under the opening 14 by theoxidation-treatment as shown in FIG. 3A.

Further, since the seed crystal layer 16 made up of silicon carbide hassufficiently low oxidation rate as compared with that of the silicondioxide layer 4 and the silicon substrate 2, an oxide layer 18 is thinlyformed only on the outside while most of the seed crystal layer 16 partremains in just the state of silicon carbide.

Incidentally, in the above oxidation treatment, the oxidation may beeffected after the silicon dioxide layer 4 is removed.

Subsequently, etching is performed using buffered hydrogen fluoride orthe like to remove the silicon dioxide layer 18 outside the seed crystallayer 16 (see FIG. 3B). Thereafter, epitaxial growth is effected withthe silicon carbide seed crystal layers 16 used as the seed crystal. Theepitaxial growth at this step is controlled so as to increase lateralgrowth and is stopped before the layers grown out of each seed crystallayer 16 come to be connected to one another, resulting in the structureshown in FIG. 3C.

An epitaxially grown layer 22, which is a silicon carbide grown layer,is isolated from the silicon substrate 2 by the field oxide layer 20.Accordingly, it generates no electrostatic capacitance due to the pnjunction with the silicon substrate 2. This means that forming devices(e.g. transistors, FETs) in each epitaxially grown layer 22 will notcause any reduction in operating speed due to electrostatic capacitance,allowing a high-speed device to be realized. Moreover, since noelectrostatic capacitance is caused due to the pn junction, a goodhigh-frequency characteristic and an enhanced latch-up characteristiccan be obtained.

Further, each epitaxially grown layer 22 is not connected to oneanother, thus causing no electrical isolation due to the pn junctionbetween the layers.

In addition, the plane bearing of each seed crystal layer 16 is uniformand, therefore, that of the epitaxially grown layer 22 is also uniform.Accordingly, the oxidation rate is uniform, facilitating the control ofdevice characteristics when forming devices in the epitaxially grownlayer 22.

Further, the form of the openings 14 may be selected as appropriate tothe required epitaxially grown layer 22. For example, they may be in theform of holes as shown in FIG. 4, or in lattice-like form as shown inFIG. 5. It may further be preferable that the direction of patterningthe silicon dioxide layer 4 be <100>, which can prevent the occurrenceof all faults.

Moreover, when the steps shown in FIGS. 2A-2E and 3A-3C are added afterthe formation of devices in the epitaxially grown layer 22 in FIG. 3C,integrated circuits can be formed as a three-dimensional structure.

Next, an embodiment to manufacture a MOS device according to themanufacturing method of the present invention will be explained. In thisembodiment, steps extending from FIG. 2A to 2E are the same as describedearlier, wherein the silicon dioxide layer 4 is formed 100 nm thick.Also, the surface of the silicon substrate 2 is carbonized by use of C₂H₂ (1150° C., 5 min. H₂ carrier gas) at the step shown in FIG. 2D beforegrowing a seed crystal layer 16. This treatment forms a buffer layer onthe surface of the silicon substrate 2, thus reducing the latticeinconsistency between silicon and silicon carbide. Thereafter, the seedcrystal layer 16 is formed by growing silicon carbide (β-SiC) with theaid of Si₂ H₆ and C₂ H₂ (see FIG. 2E). The seed crystal layer 16 in thisembodiment is grown to have a thickness of 1 μm. When inverting toN-type, N₂, PHOS or As serving as a dopant is added at this step.

Subsequently, the silicon dioxide layer 4 is removed to thereby obtainthe structure shown in FIG. 6A. In this state, oxidation is effected,which allows a field oxide layer 20 to be formed and the surface of theseed crystal layer 16 to be oxidized thinly (see FIG. 6B). When creatingan impurity layer within the silicon carbide grown layer, an ion implantis carried out after the step of FIG. 6B. Ions are preferably implantedat a temperature around 600° C. with the aim at improving the activationrate of regions involved.

Further, after removing an oxide layer 18 outside the seed crystal layer16, epitaxial growth of silicon carbide is carried out on the basis ofthe seed crystal layer 16. In this embodiment, silicon carbide is grownto be 2 μm thick by use of Si₂ H₆ and C₂ H₂ (1360° C., H₂ carrier gas,PH₃ dopant gas), thus obtaining epitaxially grown layers 22a and 22b, asshown in FIG. 6C, while ion-implanted seed crystal provides a P-typeimpurity layer 23.

Moreover, the surface of epitaxially grown layers 22a and 22b areoxidized, thereby forming oxide layers 24a and 24b, and thereafter, aninsulating layer 26 is made to grow in a region between epitaxiallygrown layers by SOG (Spin on Glass). The epitaxially grown layer 22a isnext subjected to an ion implant step, wherein aluminum ions areimplanted and then diffused to form a layer 28, resulting in thestructure shown in FIG. 6D.

Since the ion diffusion step described above requires long times andhigh temperature, N-type impurities and P-type impurities may beindependently doped at the same time while effecting the epitaxialgrowth of silicon carbide.

Next, oxide layers 24a, 24b and 26 on epitaxially grown layers 22a and22b are removed by flash-etch. Gate oxide layers 30a and 30b are thenformed. Further, polysilicon gates 32a and 32b are created. This isfollowed by the step of an ion implant and diffusion, which provides asource region and a drain region, resulting in the structure shown inFIG. 6E.

Thereafter, processes including formation of an insulating layer 34using SOG and CVD (Chemical Vapor Deposition), a polysilicon contact 36by deposition, metal wiring 38 and a protective coat 40 are performed,thus obtaining a complementary MOS and a diode, as shown in FIG. 7.

AMOS transistor in general is isolated by the LOCUS method. This method,however, is not suitable for the case where the epitaxially grown layeris made up of silicon carbide, because oxidation of silicon carbide istime-consuming as compared with that of silicon of which the oxidationrate is 10 times greater than that of silicon carbide. In the presentembodiment, on the other hand, devices are formed in epitaxially grownlayers 22a and 22b which are separated from one another beforehand,thereby overcoming the above-mentioned problem.

As a result, a device having excellent environment resistance (hightemperature resistance, radiation resistance) characteristic of siliconcarbide can be obtained easily as described above.

In the method for manufacturing a semiconductor device of the presentinvention, crystal growth is effected until the silicon carbide seedcrystal layer protrudes from the opening of the oxide insulating layer,thus obtaining a silicon carbide seed crystal layer having the sameplane bearing. Moreover, oxidation of all of the surface is carried outso that the silicon substrate under the opening is oxidized, in order tocut off the connection between the silicon carbide seed crystal layerand the silicon substrate. Subsequently, the silicon carbide grownlayer, which is formed as regions isolated from one another, is grownout of the silicon carbide seed crystal layer. As a result, a siliconcarbide grown layer can be obtained which is isolated from the siliconsubstrate, formed as regions isolated from one another, and has auniform plane bearing. In other words, the silicon carbide grown layercan be formed without involving the pn junction with the siliconsubstrate, thus providing a high-speed semiconductor device. Also, theuniform plane bearing facilitates control during the formation of devicecomponents.

In the manufacturing methods of the present invention, after the openingformation step and before the seed crystal growth step, thin polysiliconlayers or nitride silicon layers are formed on the oxide insulatinglayer of the opening sidewall. This arrangement serves to suppress anycrystal faults to the opening sidewall from occurring during the crystalgrowth.

In the methods for manufacturing a semiconductor device of the presentinvention, the steps extending from insulating layer formation to deviceformation are repeated a specified number of times on the siliconcarbide grown layer on which a semiconductor device is formed, tothereby obtain the silicon carbide grown layers insulated by a specifiednumber of oxide insulating layers. As a result, a semiconductor devicehaving a high degree of integration can be obtained as athree-dimensional structure.

In the methods for manufacturing a semiconductor device of the presentinvention, an intermediate insulating layer is provided between siliconcarbide grown layers, thereby improving insulation between siliconcarbide layers.

In the methods for manufacturing a semiconductor device of the presentinvention, the insulating layer is provided for the purpose ofinsulating a device from the silicon substrate. In addition, a device isformed in the silicon carbide grown layer which is formed as regionsisolated from one another and uniform in the plane bearing. As a result,a MOS device thus obtained is excellent in device isolation and easy tomanufacture, generating no junction capacitance during the deviceisolation process.

Although the invention has been described in its preferred form with acertain degree of particularity, it is understood that the presentdisclosure of the preferred form has been changed in the details of itsconstruction and any combination and arrangement of parts may beresorted to without departing from the spirit and the scope of theinvention as hereinafter claimed.

What is claimed is:
 1. A method for manufacturing a semiconductor devicehaving a grown layer on an insulating layer, comprising:an insulatinglayer formation step of forming an oxide insulating layer on a siliconsubstrate; an opening formation step of providing the oxide insulatinglayer with an opening for seed crystal growth; a seed crystal growthstep of effecting crystal growth until a silicon carbide seed crystallayer protrudes from said opening with the oxide insulating layer usedas a mask; a selective oxidation step of oxidizing the silicon substrateunder said opening with the silicon carbide seed crystal layer used as abarrier, thereby cutting off the connection between the silicon carbideseed crystal layer and the silicon substrate; a silicon carbide growthstep of subjecting the silicon carbide to crystal growth on the basis ofthe silicon carbide seed crystal layer, to thereby obtain regions of thesilicon carbide grown layer separated from one another; and a deviceformation step of forming a semiconductor device on the silicon carbidegrown layer.
 2. A method as claimed in claim 1, further comprising:astep of forming a thin polysilicon layer or nitride silicon layer in theoxide insulating layer of an opening sidewall after the openingformation step and before the seed crystal growth step.
 3. A method asclaimed in claim 1, wherein said silicon substrate has a plane bearingof 100, so that the insulating layer is also grown with a plane bearingof
 100. 4. A method as claimed in claim 1, further comprising:anintermediate insulating layer formation step of providing an insulatinglayer between silicon carbide grown layers.
 5. A method as claimed inclaim 1, wherein the steps from said insulating layer formation step tosaid device formation step are repeated a specified number of times onthe silicon carbide grown layer in which a semiconductor device isformed thereby to obtain a specified number of silicon carbide grownlayers insulated by said oxidized insulator.
 6. A method formanufacturing a semiconductor device having a grown layer on aninsulating layer, comprising:an insulating layer formation step offorming an oxide insulating layer on a silicon substrate; an openingformation step of providing the oxide insulating layer with an openingfor seed crystal growth; a seed crystal growth step of effecting crystalgrowth until the silicon carbide seed crystal layer protrudes from saidopening with the oxide insulating layer used as a mask; an oxideinsulating layer removal step of removing the oxide insulating layer aselective oxidation step of oxidizing the silicon substrate under saidopening with the silicon carbide seed crystal layer used as a barrier,thereby cutting off the connection between the silicon carbide seedcrystal layer and the silicon substrate; a silicon carbide growth stepof subjecting the silicon carbide to crystal growth on the basis of thesilicon carbide seed crystal layer, to thereby obtain regions of thesilicon carbide grown layer separated from one another; and a deviceformation step of forming a semiconductor device on the silicon carbidegrown layer.
 7. A method as claimed in claim 6, further comprising:astep of forming a thin polysilicon layer or nitride silicon layer in theoxide insulating layer of an opening sidewall after the openingformation step and before the seed crystal growth step.
 8. A method asclaimed in claim 6, wherein said silicon substrate has a plane bearingof 100, so that the insulating layer is also grown with a plane bearingof
 100. 9. A method as claimed in claim 6, further comprising:anintermediate insulating layer formation step of providing an insulatinglayer between silicon carbide grown layers.
 10. A method as claimed inclaim 6, wherein the steps from said insulating layer formation step tosaid device formation step are repeated a specified number of times onthe silicon carbide grown layer in which a semiconductor device isformed thereby to obtain a specified number of silicon carbide grownlayers insulated by said oxidized insulator.